1. Field of the Invention
The present invention generally relates to an electrets touch device, and more particularly to a 3-dimension non-bias electrets multi-touch device capable of determining coordinates of first and second directions of an external force and quantifying the external force in the third direction.
2. Description of Prior Art
With the progress of modern technology, the life quality significantly gets better than ever and the consumable electronic products are presented to the public so rapidly. A touch control device which is a kind of input interface for a better humanity design and combining the display has been developed. Such touch control device makes interactions of the human interface device friendlier and also more accurate. A Finger or a stylus can be utilized to click and input via function indications shown on the display of the touch control device. Even directly writing or painting by the finger or the stylus can be realized almost without any learning. Moreover, such touch control device combining the display occupies less space and appearance of an electronic product than the traditional input interface, e.g. keypad or mouse. Such touch control device fits in with miniaturization trend of the consumable electronic products in this modern time. Therefore, such touch control device replaces other types of input interfaces and gradually becomes a main stream recently in PDA, PND, mobile phone, notebook, ATM and etc. Furthermore, the multi-touch function presented by iphone of Apple company in 2007 starts a tremendous campaign about developing and researching the touch control device in the related industries. Since then, related technologies progresses so rapidly. The mobile phones published recently by the famous mobile phone manufacturer, Nokia, also utilize the touch control device for the input interface. It seems that the touch control device will become a standard interface for the Nokia mobile phone definitely.
The touch control technique in development comprises Optics, ultrasonic, electromagnetic, resistive and capacitive touch devices. The resistive and capacitive touch devices are the main stream techniques and well-developed thereamong. The resistive touch device is mainly applied in low-price products, such as, consumer mobile phones, PDA, PND and etc. The capacitive touch device is generally applied in high-price products, such as ATM, industry equipments and etc. For example, the second generation TouchSmart PC of HP company and the iphone of Apple company both utilize the capacitive touch device as being the touch pads. However, the surface of the resistive touch device is easily scratched and the sensitivity is worst so that a larger contact pressure is necessary for detection. The capacitive touch device has higher sensitivity but the manufacture processes are more complicated. Besides, there is also a drawback of the capacitive touch device existing. That is, non-conductive objects, such as, a stylus and a fingertip cannot be utilized for inputting operation.
In the U.S. Pat. Nos. 6,819,316B2, 7,030,860B1 and 7,154,481B2, capacitive touch devices are disclosed to detect touch coordinates according to capacitance change caused by a deformation due to contact pressure. Meanwhile, the disclosed capacitive touch devices are also flexible. In the U.S. Pat. Nos. 7,260,999B2 and 7,511,702B2, capacitive touch devices are disclosed to detect the touch coordinates and external force strength according to capacitance change caused by the deformation due to the contact pressure. However, what is disclosed is that the touch coordinates and the external force strength are detected by different sensing circuits. Moreover, for all the capacitive touch devices disclosed in the aforesaid patents, extra bias voltages are necessary to be provided between upper and lower substrates of the capacitive touch devices for touch control function. Accordingly, the circuits and the physical structures of the capacitive touch devices must become more complicated. The extra bias voltages will also cost a certain power consumption to lead the usage time of the electronic product inextensible. Considering the miniaturization trend of the consumable electronic products in this modern time, the short usage time is a principal factor that the consumable electronic products cannot be popular.